tty: baudrate: Explicit usage of B0 for encoding input baudrate

Function tty_termios_input_baud_rate() checks IBSHIFT & CBAUD against B0
constant to determinate if input speed equals to output speed. So do same
B0 check also in tty_termios_encode_baud_rate() function to make these two
functions compatible.

Currently macro B0 is defined to 0 so there is no functional change.

This change just make code more explicit to show that Bnnn constants are
stored in CBAUD.

Signed-off-by: Pali Rohár <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/tty/tty_baudrate.c

···
 	termios->c_ospeed = obaud;
 
 #ifdef IBSHIFT
-	if ((termios->c_cflag >> IBSHIFT) & CBAUD)
+	if (((termios->c_cflag >> IBSHIFT) & CBAUD) != B0)
 		ibinput = 1;	/* An input speed was specified */
 #endif
 #ifdef BOTHER